Troubleshooting Brake Controller Installations

Even the most experienced installer will encounter it from time to time: the brake controller installation is finished, the wires have all been run, but something is going wrong. Whether your controller is showing an error message or the trailer brakes just aren't working, there are a number of troubleshooting techniques you can use to get the problem fixed and get back on the road. Using the following information and testing procedures, you should be able to pinpoint and eliminate the most common issues encountered during and after a brake controller installation.






Common Brake Control Issues


ProblemPossible IssuesTesting Procedures
Brake controller display does not show that trailer is connected.
  1. Short on brake signal wire, trailer or vehicle side.
  2. Corrosion in trailer and/or vehicle plug.
  3. Short on brake magnets on trailer.
  4. Malfunctioning brake magnet(s).
Brake controller loses connection to battery ground.
  1. Ground wire was not connected to negative battery terminal, ground area does not have solid connection to ground.
  2. Adapter wiring does not match OEM connector on vehicle.
  3. Ground connection to negative battery terminal is loose.
  4. Ground wire has been damaged and exposed wiring is touching a metal area.
Brakes are applying too aggressively for the brake controller settings.
  1. Brake assemblies are not properly adjusted.
  2. Boost/Gain on brake controller is set too high for trailer size.
  • Adjust brakes properly (see video).
  • See brake control owner's manual for proper boost/gain settings for trailer size.
Trailer brakes only work with manual control, not with brake pedal. (Be sure to test for proper brake controller function with unloaded trailer in a safe area where you can reach low road speed before you determine that the brake controller is not working)
  1. Incorrect stoplight wire connection.
  2. Adapter wiring layout does not match OEM connector on vehicle.
Brake controller detects an overload condition during use.
  1. Trailer has too many brakes for brake controller to handle.
  2. Corrosion in trailer and/or vehicle plug.
  3. Brake signal wire on trailer is damaged, exposed wiring is touching metal area or another circuit.
  4. Malfunctioning brake magnet(s).
Display is erratic while braking.
  1. Short to battery on 12V wire connection.
  2. Short on brake signal wire, trailer or vehicle side
  3. Corrosion in trailer and/or vehicle plug.
  4. 12V wire was not connected to vehicle battery, 12V source used is not constant.
Brake controller detects a short on the brake wire while vehicle is idling.
  1. Corrosion in trailer and/or vehicle plug.
  2. Brake signal wire on trailer or vehicle is damaged, exposed wiring is touching metal area.
Trailer brakes engage when it is plugged into the vehicle.
  1. Incorrect stoplight wire connection.
  2. Corrosion in trailer and/or vehicle plug.
  3. Adapter wiring does not match OEM connector on vehicle.
Brake controller does not turn on.
  1. Connection to battery is not complete.
  2. Vehicle is missing a fuse or relay required to power 12V power circuit.
  3. Adapter wiring layout does not match OEM connector on vehicle.
  • Method 1
  • Check fuse block for missing fuse/relay. See vehicle-specific FAQ if available, or check owner's manual.




Basic Testing Procedures


Method 1: Verifying Correct Wire Connections (Hard Wire Installs)

Testing the Stoplight WireBrake Control Wire Colors








Wiring Adapter vs. OEM Connector

Method 1: Verifying Correct Wire Connections (Plug-in Installs)









Method 2: Testing for the Brake Signal

Testing the Blue Wire






Method 3: Looking for a Short or Ground Issue

Damaged Wiring








Method 4: Inspecting the Brake Assemblies

Brake Magnets





For more information, see:


Updated by: Raymond P.

Last updated: 7/5/18







Departments

Towing

Sports and Recreation

Trailer Parts

Vehicle

What our customers are saying:

The people answering the phones were professional & knowledgeable. All this and the best prices on the internet, How can you go wrong?

Bill

Vero Beach, FL

Popular Vehicles